Beijing: The crew of a Chinese search plane has spotted "suspicious objects" floating in the southern Indian Ocean on Monday while searching for missing Malaysia Airlines flight MH370 off Australia, according to official news agency Xinhua.

The crew has reported the co-ordinates to the Australian command centre as well as Chinese icebreaker Xuelong, which is en route to the search area and should arrive at about 4am AEDT on Tuesday morning. Reports indicate the floating objects include "white and rectangular" items.

Among the floating objects sighted, the Xinhua report said, were two larger items and a number of smaller white fragments scattered over an area of a "few kilometres".

Royal Australian Air Force Flight Engineer, Warrant Officer Ron Day keeps watch for any debris as he flies in an AP-3C Orion over the Southern Indian Ocean. Photo: Reuters

The Chinese planes left Perth's RAAF Pearce base for the search zone about 8.45am and 9.20am AEDT. Taking into account a four-hour flight time, the first plane would have started searching shortly before 1pm. Eight other planes - from Australia, the United States, Japan and New Zealand - are involved in the search and the Chinese have asked that some be diverted to the area of the latest sighting.

The search is believed to be focus on two areas of 59,000sq km and 68,500 sq km.

HMAS Success is also near the search area, while a number of Chinese ships are en route.

The pace of the discovery could suggest Chinese authorities had more information about their satellite image than they have made public, aviation expert and editor of Airlineratings.com Geoffrey Thomas said.

"We are yet to get the precise detail of what it is that they've seen but it just adds to the growing weight of evidence that theres something out there," he said.

"It's one more piece in a jigsaw puzzle, and it's a major piece."

Mr Thomas believes the Chinese set a course on Monday morning based on the coordinates of the image one of their satellites captured last week.

"My understanding is that they have gone and searched for the specific targets they took images of that were released on Saturday," he said.

"They may have more intelligence about it than they've revealed, it's possible, and I think the visual imagery that we've been given are degraded images in the first place.

"You get a truckload more clarity out of Google Earth than you do out of these satellite images."

But a person close to the Chinese search effort said there was nothing unusual about the speed of the discovery.

"The process of information regarding all of these possible sightings has to go through so many different sets of eyes that the information from all sources, Australian, Japanese, Chinese is not reaching the

public in a way that was originally expected," the source said.

"But there is no way that there is anything underhand from the Chinese government, that has approached this event with such an open and intense determination to find a resolution."

The focus of the multinational search shifted to the southern Indian Ocean after Australia said last week that satellite imagery had identified suspicious debris that might be linked to the missing plane.

China and France have since released further satellite imagery over the weekend showing suspicious objects in the same region which could be linked to the missing Malaysia Airlines flight. There was also a reported sighting of a floating wooden pallet and strapping belts in the area.

The plane, which went missing on March 8, had 239 passenger and crew onboard, including six Australians.

The United States Navy earlier announced it would send a state-of-the-art black box finder to the search area.

The Navy's Pacific Command, based in the Philippines, is moving the sophisticated equipment into the area "as a precautionary measure in case a debris field is located".

The "Towed Pinger Locator 25" is a hyper-sensitive hydrophone that the Navy claims can locate black boxes on commercial aircraft down to a maximum depth of 6000 metres anywhere in the world.

The locator, which is towed behind a vessel at slow speeds, carries a passive listening device for detecting pingers on black boxes that automatically transmit an acoustic pulse. The pulse only lasts for 30 days.

"This movement is simply a prudent effort to preposition equipment and trained personnel closer to the search area so that if debris is found we will be able to respond as quickly as possible since the battery life of the black box's pinger is limited," said Commander Chris Budde from US Seventh Fleet Operations.

If found, the acoustic signal of the pinger is transmitted up the cable and is presented audibly. The operator monitors the greatest signal strength and records the navigation coordinates. This procedure is repeated on multiple track lines until the final position is triangulated.